An important new study shows that a child will most likely be healthier throughout her childhood if a tax on cigarettes is in place when her mother is pregnant. Economist David Simon (who, full disclosure, is my cousin) at the University of Connecticut has extended the findings that the health of infants can be improved by a policy intervention that improves the in-utero environment, and has provided strong evidence that cigarette taxes can improve the health of children into their teen years.

It is well established that smoking during pregnancy can harm a developing fetus. In his paper, Simon cites studies that demonstrate the negative effects of taxes on cigarette smoking, and in a second paper, he collects and reviews the literature that shows that pregnant women are responsive to cigarette taxes. Simon uses a restricted-use version of the National Health Interview Survey, which the Centers for Disease Control and Prevention has used since 1957 to collect data on the health of the U.S. population, to examine medium-term childhood health outcomes for individuals exposed to a cigarette tax in-utero.

The findings are striking. With a one dollar increase in a state cigarette tax, Simon saw a 10% decrease in sick days from school and a 4.5% decrease in the likelihood of having two or more doctor visits within the last twelve months. He also noted that there was “suggestive evidence” for decreases in emergency room visits, hospitalizations, and asthma.

In short, and very simplistically, a tax on cigarettes causes more people, including and especially pregnant women, to stop smoking. This is turn results in healthier newborns, babies, and children. Policy intervention, successful!

What can we learn from this study, and others in the same area, about what policy interventions may be effective to decrease the negative health effects of obesity on children? After all, there has been some noise around the idea that “big food” should be treated like tobacco, and that we should model our anti-obesity efforts on the anti-smoking campaigns that have been successful over the last few decades.

But what we learn, of course, from these studies, is just how difficult such studies are to run, and how hard it is, therefore to evaluate the success of policy interventions. Before Simon could evaluate the effect of cigarette taxes on medium-term health outcomes, he needed to know that (1) smoking during pregnancy affected the fetus in specific ways, and (2) pregnant woman were responsive to cigarette taxes. His study is built on these basic premises, which took decades to establish. We have no such foundation in the obesity context.

The causes of obesity are complicated and interdependent, and the same goes for its effects on the human body. This makes designing and evaluating policy interventions challenging. Sure enough, the research needed to buttress our understanding of the causes of obesity, the effects of obesity, and the effects of various policy interventions is ongoing. Our understanding, however, of the causal connection between food items, including sugary sweetened beverage, and obesity is imperfect. Scholars are conducting exciting and important research on the relationship between policy interventions and health outcomes in the food context. But we need to be patient.